(PERTH, Australia) -- Another "possible signal" has been detected in the search for missing Malaysia Airlines Flight 370, which disappeared on March 8 with 239 people on board.

In a statement Thursday, retired Australia Air Chief Marshal Angus Houston said that an aircraft detected a possible signal near the Australian vessel Ocean Shield during an acoustic search Thursday afternoon.

"The acoustic data will require further analysis overnight but shows potential of being from a man-made source," Houston noted.

The latest discovery comes after four signals consistent with the pings of a plane's black box were detected in the southern Indian Ocean. The first two were heard last Saturday and the second two on Tuesday afternoon and evening.

Time is running out to find the Boeing 777's black boxes, whose locator beacons have a battery life of about a month.